package tree.反转二叉树;
//给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。 
// 示例 1： 
//输入：root = [4,2,7,1,3,6,9]
//输出：[4,7,2,9,6,3,1]
// 示例 2： 
//输入：root = [2,1,3]
//输出：[2,3,1]
// 示例 3： 
//输入：root = []
//输出：[]
// 提示： 
// 树中节点数目范围在 [0, 100] 内 
// -100 <= Node.val <= 100 
// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 👍 1990 👎 0


//leetcode submit region begin(Prohibit modification and deletion)

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {
    }

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

public class Solution {
    public TreeNode invertTree(TreeNode root) {
        return invertTreeDp(root);
    }

    public TreeNode invertTreeDp(TreeNode node) {
        if (node == null){
            return node;
        }
        TreeNode left = invertTreeDp(node.left);
        TreeNode right = invertTreeDp(node.right);
        node.left = right ;
        node.right = left;
        return node ;
    }
}

